What’s the thing you keep forgetting to tell kids?

I was helping a new kid pack his bag yesterday, and he asked me why the pen he’d been using for weeks had a weird wobble in the grip. I didn’t know what to say—just that some pens are built for hands that haven’t learned how to hold them yet. Then I realized: we never teach that. We hand them tools and expect them to figure out how to cradle a pencil like they were born to it. So what’s the quiet thing you’ve learned about small bodies and big worlds that you keep forgetting to pass on?